textproduct: Albany

WHAT HAS CHANGED

Continued trend to slow down PoPs with the showers this afternoon with only slight or low chances along and west of the Hudson River Valley prior to sunset.

Lowered max temps on Tue about 3-4 degrees below the NBM blending with with NBM and MAVMOS guidance with back door cold front and clouds through the day. Lowered PoPs into chance category for showers/slight chance of thunderstorms for Tue-Tue early evening with a brief break with short-waves with any Marginal severe threat south and west of the Capital Region.

Unsettled pattern continues through the mid week with additional chances for strong storms possible Wed-Thu with heavy rainfall and at least isolated flash flooding, although there remains some uncertainty in exactly how things will evolve this week with the frontal boundary location.

KEY MESSAGES

1) A low pressure system and a warm front brings showers and non- severe thunderstorms tonight into early Tue with locally heavy rainfall.

2) A few strong to severe thunderstorms south and west of the Capital Region Tue afternoon into the evening with an isolated flash flood threat for the region.

3) Additional rounds of showers and thunderstorms through the mid week with potentially some strong thunderstorms on Wed with isolated to scattered instances of heavy rainfall/ flash flooding possible due to a stalled frontal boundary.

DISCUSSION

KEY MESSAGE 1...High pressure builds in from southwest Quebec with some patchy fog and stratus this morning that will burn off in the late morning. The mid and upper level flow will be west to northwest the next several days, as upstream ridging sets up over the Upper Midwest, Great Lakes Region and Ontario with a strong closed H500 anticyclone centered over the Lower MS and TN Valleys. The cold front from this morning will slowly lift back to north/northeast from PA/NJ and western NY with increasing clouds and showers building in from the west/southwest in the mid to late afternoon. We slowed down the PoPs/showers based on the latest short-range guidance and CAMS. Temps will be seasonable today with upper 60s to upper 70s across the region with moderate humidity levels with dewpoints in the upper 50s to mid 70s.

Tonight, the isentropic lift increases ahead of the warm front and a short-wave rolls across the ridge into upstate NY. A wave of low pressure or decaying MCS rides along the boundary bringing periods of showers and some thunderstorms due to elevated instability /Showalter stability indices below 0/ ahead of the front and wave. Latest HREF guidance indicates mean MUCAPEs generally 500 J/kg or less with 0-6 km shear 35-40 KT. With the parcels elevated we are not expecting severe thunderstorms. Rainfall could become moderate to locally heavy with PWATs rising into the 1.5-2.0" range about 1 to 2 STDEVs above normal. The CAMs have shifted slightly further south with the coverage of the showers and thunderstorms with the most widespread coverage from the Mohawk Valley/Capital Region southward, but slight variations may occur. Ponding of water on roadways may occur in a few spots. Gridded FFG values remain high right now with drier weather recently. WPC maintains a Marginal Risk (Level 1 of 4) in their Day 1 ERO. An isolated flash flood threat can not be ruled out in case any training occurs, but that looks low on the onset. The rainfall should diminish Tue morning from west to east. Low temps will be muggier in the mid 50s to lower 60s.

KEY MESSAGE 2...SPC has maintained a Marginal Risk (Level 1 of 5) for severe t-storms for locations south and west of the Greater Capital Region/Berkshires. The areas highlighted are the eastern Catskills, mid Hudson Valley, southern Taconics and NW CT as well as the western Mohawk Valley of southern Herkimer County. It is a tricky forecast to see where the warm front/boundary sets-up, as some of the guidance like the GFS/NAM show the boundary stalling south of the Capital Region with the front acting like a backdoor cold front, as sfc ridging builds back in from southeast Quebec and northern New England. The forecast area could be caught in clouds most of the day with north/northeast winds especially from the I-90 corridor north. However, the latest HREF guidance does show the best 0-6 km deep shear of 40-45 KT with mean SBCAPEs of 1000-1500 J/kg overlay for the south/southwest zones in the Marginal Risk. Mid level lapse rates look decent towards I-84. Some deep organized convection could form with some diurnal heating on the warm side of the boundary or outflow boundaries with strong to severe thunderstorms with damaging winds and large hail, as well as locally heavy rainfall due to the above normal PWATS. The severe threat looks to be in the mid afternoon into early evening. We kept PoPs in the chance to low likely range (35-60%) prior to midnight.

Another ridge roller disturbance looks to arrive for Wed with a more robust heavy rain/flash flood threat and additional strong to severe thunderstorms. Nonetheless, WPC maintains a Marginal Risk in the Day 2 ERO for Tue-Tue night across the forecast area. Max temps were lowered some on Tue below the NBM with the clouds and back door front likely south of Albany. We leaned closer to an NBM/MAVMOS blend. We did not go as cool as the METMOS values. Highs in the mid 60s to mid 70s will be common from the Capital Region north and 70s to around 80F south.

KEY MESSAGE 3...A strong short-wave in the west/northwest flow around the rim of the ridge arrives for WED. The frontal boundary attempts to lift back to north/northeast across the region. The 0-6 km shear is strong, but the instability looks elevated initially. However, if we break into a warm sector some strong to severe convection could form with the MCS/wave with moderate to large instability. The threat for strong storms looks like it would be greatest from the Capital Region southward. SPC with the latest Day 3 has most of the region in general thunder with a Marginal Risk (Level 1 of 5) just grazing Ulster County for an isolated severe threat.

Strong theta-e advection occurs with the wave with PWATs remaining 1 to 2 STDEVs above normal. Any training of cells or back building could yield some isolated to scattered instances of flash flooding. WPC has locations mainly south/southwest of Albany in a Slight Risk (Level 2 of 4) for potential scattered instances of flash flooding and a Marginal Risk (Level 1 of 4) to the north and east. We will have to see where the heavier rainfall totals occur prior to Wed, as soils may start to get saturated. At the very least urban and poor drainage flooding/minor flooding could occur in some locations. A Flood Watch may also be needed for parts of the region in the future. The 01Z/NBM 24-hr probabilities for the period ending 12Z/Thu for >1" rainfall are 50-80% across eastern NY and western New England. The probs for 2" or greater are mainly less than 25% for most of the region, except the Mohawk Valley/southwest Dacks where they are as high as 45-60%. This heavy rain threat bears watching. It will remain muggy and humid with near normal temps.

The cold front moves through Thu with additional chances of showers and thunderstorms with some locally heavy rainfall again. The mid and upper level trough moves across the region for a isolated to scattered showers continuing into Friday before cooler, less humid and drier weather is expected for the holiday weekend.

AVIATION /12Z MONDAY THROUGH FRIDAY/

VFR conditions continue at KALB, KPSF, and KPOU through 01/00z. Patchy fog has developed at KGFL this early morning and should diminish by 13z with VFR conditions returning. For after 01/00z, chances for rain showers arrive at all TAF sites through the end of the TAF period so continued the mention of light rain shower activity in either PROB30s or the prevailing depending on forecast confidence at this time before 01/06z. Confidence is higher for KALB after 01/01z, with lower confidence at KGFL, KPSF, and KPOU after 01/00z. Then confidence increases for TAF sites to begin seeing rain shower activity after 01/06z with MVFR/IFR conditions.

Winds continue to be light and variable expect for KPSF where west to northwest winds between 5 and 10 knots continue through 09z when winds should become calm. Light and variable winds continue throughout the TAF period.

Outlook...

Tuesday Night: High Operational Impact. Likely SHRA. Wednesday: High Operational Impact. Definite SHRA...RA...TSRA. Wednesday Night: High Operational Impact. Definite SHRA...TSRA. Thursday: Moderate Operational Impact. Chance of SHRA...TSRA. Thursday Night: No Operational Impact. NO SIG WX. Friday: Moderate Operational Impact. Chance of SHRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.